The convenience, efficiency, and safety of weight-training exercise machines is widely recognized. Popular weight-training exercise machines feature multiple stations at which a user may perform a variety of exercises for developing and toning different muscle groups. For example, an exercise machine may include a “press” station for exercising the chest and shoulders, a leg station for exercising the legs, and a pull-down station for exercising the arms and upper body, or other training stations. Exercise machines typically include a weight stack that may provide a variable training load. The user simply adjusts the position of a pin to attach a desired number of weight plates to a cable-and-pulley device to achieve a desired training load.
FIG. 1 is an isometric view of an exercise machine 100 having four exercise stations (or “user interface” stations): a press station 102, a leg curl station 104, a low pull station 106, and a high pull station 108. The exercise machine 100 includes a frame 139 and a cable-and-pulley device 120 that operatively attaches each of the exercise stations to a weight stack 112. In operation, a user (not shown) may perform, for example, a press exercise by lying on a seat 114 and grasping a pair of handles 116. The user than applies a training force to the handles 116 by pressing the handles 116 away from the user's chest. The training force is transmitted through the cable-and-pulley device 120 and applies a lifting force on at least a portion of the weight stack (a training load) 118. As the user overcomes the gravitational force on the training load 118, the handles 116 are displaced and the training load 118 is raised. Exercise machines of the type shown in FIG. 1 are disclosed, for example, in U.S. Pat. No. 4,986,538 to Ish, incorporated herein by reference.
FIG. 2 is a schematic view of the cable-and-pulley device 120 of the exercise machine 100 of FIG. 1. The cable-and-pulley device 120 includes a first cable 122 attached to the training load 118 and to the high pull station 108. The first cable 122 is trained about a first end pulley 124 proximate the high pull station 108, a first intermediate pulley 126, a first upper pulley 128 of a first double-floating pulley 130, and a main pulley 132 positioned over the training load 118. As used herein, the designation “end pulley” refers to a pulley that is located immediately adjacent to a user interface station, while “intermediate pulley” generally refers to a pulley that is not an “end pulley.”
The cable-and-pulley device 120 also includes a second cable 132 that is attached to the low pull station 106 and is trained about a second end pulley 134 and a first lower pulley 129 of the first double-floating pulley 130. The second cable 132 also is trained over a second intermediate pulley 136, a third intermediate pulley 138, a fourth intermediate pulley 140, and a second upper pulley 142 of a second double-floating pulley 144. An end 146 of the second cable 132 is fixed in a stationary position. A third cable 148 is attached to the leg curl station 104 and is trained over a third end pulley 150, a fifth intermediate pulley 152, a second lower pulley 143 of the second double-floating pulley 144, a fourth end pulley 154, and finally, is attached to the press station 102.
Cable stops 156, 158, 160, 162 are attached to the cables 122, 132, 148 proximate each of the end pulleys 124, 134, 150, 154. FIG. 3 is an enlarged, partially exploded view of a cable stop 156 attached to the first cable 122 of the cable-and-pulley device 120. The cable stop 156 includes a stop ball 159 having a bore 161 therethrough. The first cable 122 is passed through the bore 161. A flanged ball 163 is then positioned on the first cable 122 and is swaged or otherwise fixed into position. The stop ball 159 is then slid back along the first cable 122 into engagement with the flanged ball 163, locking the stop ball 159 into position. A free end 123 of the first cable 122 continues on through the flanged ball 163 for attachment to a pull handle 109 (see FIG. 1) of the high pull station 108. A variety of other cable stop configurations may be used, including “genie bottle”-shaped stops.
As described in U.S. Pat. No. 4,986,538, the cable stops prevent retraction of the cables through the end pulleys as one of the user interface stations is being used. For example, when the user performs the press exercise as described above, the cable stop 160 is drawn into contact with the third end pulley 150 and a portion of the frame 139. The tension in the third cable 148 pulls downwardly on the second double-floating pulley 144, creating tension in the second cable 132 that draws the cable stop 158 into contact with the second end pulley 134. In turn, the tension in the second cable 132 pulls downwardly on the first double-floating pulley 130, creating tension in the first cable 122. The tension in the first cable 122 draws the cable stop 156 into contact with the first end pulley 124, and lifts the training load 118.
Beneficial results have been achieved using the cable-and-pulley device 120 and the exercise machine 100. Generally, however, virtually all exercise machines that use cable-and-pulley devices experience a characteristic stretching of the cables as the user applies a training force at one of the user interface stations. In some instances, the stretching of the cables may be imperceptible to the user. The stretching of the cables may become more perceptible to the user, however, as the number of cables in the cable-and-pulley device increases, as the length of the cables is increased, or as the magnitude of the training load is increased. Thus, the stretching of the cable may detract from the user's satisfaction, or may adversely impact the performance of the machine.